Method for improving end seams in containers with a fin-type back seam by double heat sealing



Aprll 14, 1970 c. G. BAUMANN. 3,5

METHOD FOR IMPROVING END SEAMS IN CONTAINERS WITH A FIN-TYPE BACK SEAM BY DOUBLE HEAT SEALING Filed Dec. 20, 1966 INVENTOR. Carl G. Buumonn ATTORNEYS United States Patent METHOD FOR IMPROVING END SEAMS IN CON- TAINERS WITH A FIN-TYPE BACK SEAM BY DOUBLE HEAT SEALING Carl G. Baumann, Dayton, Ky., assignor to The Procter & Gamble Company, Cincinnati, Ohio, a corporation of Ohio Filed Dec. 20, 1966, Ser. No. 603,298 Int. Cl. B31f 1/00 US. Cl. 156-226 3 Claims ABSTRACT OF THE DISCLOSURE A method for forming a liquid tight end seam on containers having a protruding fin-type back seam by sealing the end seam with one face of the fin-type seam against the end seam, and then, repositioning the fin-type seam 180 so that the other face lies against the end seam and re-sealing the end seam.

This invention relates to a process for improving the end seams on containers or packets fashioned from a flexible web of stock having a protruding fin-type back seam and end seams formed by sealing marginal portions held in face to face relationship.

Containers of this type can be fashioned from a flat web of flexible stock by first forming the stock into a tubular shape and placing the marginal edge portions in face to face relationship on their inner surface. Heat sealing the marginal portions results in theformation of a seam extending longitudinally along and projecting away from the tube. The longitudinal seam is referred to herein as a fin-type back seam. The tubular material can be formed into a packet by sealing the two ends on their superposed inner surfaces. Relatively thin, flat pouches result if the two ends are sealed in a common plane; whereas, if the end seams are placed in planes disposed at 90 to each other, a tetrahedron having four triangular faces of the same size is formed.

Containers of the above-mentioned type wherein there is a protruding fin-type back seam and end seams are especially useful for holding liquids because none of the raw edges of the stock material are exposed to the con tents of the container, and, therefore, wicking of the contents is not possible. While such containers are very useful for holding liquids, the use of these containers for certain very mobile liquids, for example cooking oil, has been limited. The reason for this is that it is extremely difiicult to make an adequate seal on the end seams where the fin-type back seam crosses the end seam, and mobile liquids will tend to leak from the imperfect seal. Heretofore, it has been diflicult to form an adequate seal at the point of intersection of the back seam and the end seam because of the hump formed by the extra overlapped layers of stock material.

An object of this invention is to provide a method of improving the end seam on containers having a protruding fin-type back seam.

It is another object of this invention to provide a method for forming end seams on containers of the type hereinbefore described which are not susceptible to leakage at the intersection of the back seam and the end seam.

The nature and substance of the invention can be briefly summarized as a two step method of making a leakproof end seam on containers having a protruding fin-type back seam. The method comprises the steps of folding the fintype seam flat against the container and forming an end seam in the container material, and as a second step, folding the fin-type seam approximately 180 so that the other face of the fin-type seam lies flat against container 3,506,516 Patented Apr. 14, 1970 fin-type back seam during the sealing of the end seam;

FIGURE 4 diagrammatically illustrates the second step of sealing the end seam wherein the protruding fin-type back seam is re-positioned and the end seam is resealed.

FIGURE 5 is a perspective view of a completed container wherein the end seams have been placed in a common plane.

There is shown in FIGURE 1 the end of a flat web 10 of stock which is a thin flexible material which can be heat sealed on the face 10a' only. Suitable stocks can be laminates or coated materials. These stocks are normally supplied in a roll, not shown in the drawings, which is unrolled to provide a continuous Web of material, a portion of which is shown at 10. In order to form a tubular member as at 11 from the web 10 the two longitudinal edges of the web are brought together so that the inside faces of marginal portions adjacent opposite edges are in contact in a face to face relationship. The marginal portions are heated under pressure, i.e., heat sealed, to form a longitudinal fin-type seam 12. Thus, the marginal portions of the web are sealed together with their inside face in superposed relationship. The web may be cut off at any desired point, resulting in a tubular member 11 of a desired length which appears in cross-section as in FIGURE 2.

Details of the method of this invention for forming an improved end scam in a tubular member 11 having a protruding fin-type back seam 12 are shown in FIGURE 3 and FIGURE 4. In the first step of the sealing operation as represented by FIGURE 3, the marginal portions of the walls of a tubular member 11 are brought together and sealed by applying heat and pressure. In this case heat and pressure are supplied by the upper jaw 13 and the lower jaw 14 of a heat sealing device clamped together to form an end seam 15 (FIGURE 5). During this sealing operation, the face of the fin-type seam 12 lies flat against the tubular member 11 (FIGURE 3). The jaws 13 and 14 of the heat sealing device are then parted and the fin-type back seam 12 is folded over 180 so that the other face of the fin-type seam 12 lies flat against the tubular member 11. As a second step the jaws 13 and 14 of the heat sealing device are clamped together on the end seam 15 (FIGURE 4) to apply heat and pressure and the end seam 15 is re-sealed with the fin-type seam 12 in its new position.

The re-positioning of the fin-type back sea-m 12 is a necessary element in the above-mentioned process of forming an improved end seal. As can be seen from the illustrations in FIGURES 3 and 4, at the intersection of the fin-type seam and the end seam there is a build-up of four layers of stock material. As mentioned hereinbefore, it is diflicult to form an adequate seal where the back seam intersects the end seam because of the extra layers of stock material. By re-positioning the fin-type back seam 12, this weak portion of the end seam 15 is exposed, and gaps left during the first seal ng operation because of the overlapping of four layers of material are bridged in the second sealing operation.

It is at this stage in the formation of a container, i.e., when the first end seam has been formed, that the container is normally filled. After the tubular member is filled, the other end is closed by bringing together the marginal portions of the walls of the tube at the open end thereof and sealing them together to form an end seam 16 in the manner hereinbefore described.

By placing the end seal 16 in a plane common to the end seam 15, a container, such as shown in FIGURE 5, which takes the form of a relatively thin packet results. If this latter end seam is placed in a plane disposed substantially 90 with respect to the other end seam, a container of greater capacity which takes the form of a tetrahedron results.

Stocks useful in the process of this invention are those which are heat scalable and consist of two or more films or layers of different materials. Useful stocks can be a wide variety of laminated products, for example, a polyethylene, polypropylene, polyvinylchloride, polyvinyl acetate, nylon, polyester, or other thermoplastic film or layers laminated to paper, fabric, aluminum foil, lead foil or other suitable flexible packaging materials and combinations thereof,

It is, of course, preferable that the stock be of a type which is sealable on one side only. If this were not the case, the protruding fin-type back seam 12 would be sealed to the container when the end seam is formed, and could not be easily repositioned on its other face for rescaling. Two especially preferred laminated stock materials heat scalable on one side only which are useful in the process hereinbefore disclosed are a laminate consisting of successive layers of non-heat scalable cellophane, polyethylene, aluminum foil and polyethylene, and a. laminate consisting of successive layers of paper, polyethylene, aluminum foil and polyethylene.

Heat sealing devices for accomplishing the sealing operations of this invention are those capable of supplying heat and pressure, and can be of the usual type which have the normal hot-bar, impulse, or high frequency sealing jaws. For use in the process hereinbefore described, it is preferred that these heat sealing devices have resilient sealing jaws. Such heat sealing devices are well known in the art.

While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention, and it is intended to cover by the appended claims all such changes and modifications that are within the scope of this invention.

What is claimed is:

1. A method of forming an end seam on a tubular member formed from thin flexible web material that is heat sealible only on its inner surface, said tubular member having a longitudinal outwardly protruding fin-type seam formed by bringing together the longitudinal edges of the web material in face to face relationship and sealing said edges to form the longitudinal fin-type seam, said method comprising the steps of bringing together the transverse end of the tubular member and folding down the fin-type seam fiat against the surface of the tubular member intermediate the extremities of said transverse end, forming an end seam at said transverse end by applying heat and pressure thereto, folding over the fin-type seam approximately so that it lies flat against the end seam, and applying heat and pressure to the end seam a second time to form a liquid tight joint at the intersection of the fin-type seam and the end seam.

2. The method of claim 1 wherein the flexible stock is a laminate heat scalable on one side only consisting of successive layers of non-heat scalable cellophane, polyethylene, aluminum foil, and polyethylene.

3. The method of claim 1 wherein the flexible stock is a laminate heat scalable on one side only consisting of successive layers of paper, polyethylene, aluminum foil, and polyethylene.

References Cited UNITED STATES PATENTS 9/1961 Meister 156-304 X 12/1965 Schirmer 156-217X SAMUEL W. ENGLE, Primary Examiner 

